The invention relates in general to a system for transferring payloads between two orbiting space vehicles. More specifically, the invention relates to a tether system that is used to transfer payloads from one orbiting space vehicle to another orbiting space vehicle.
Space vehicles in long term Earth orbit, such as the International Space Station (ISS), require periodic deliveries of payloads in order to replenishment supplies and provide replacement equipment. Conventional methods of accomplishing payload delivery require the use of a transfer vehicle, such as the Space Shuttle, to hard dock with the orbit vehicle during payload transfer. Hard docking between two space vehicles, however, requires extremely precise maneuvering to avoid damaging the fragile structures of the vehicles. The difficulties and dangers become most apparent when the visiting vehicle is an unmanned spacecraft, wherein a failure of automatic docking can result in collision between the vehicles.
In addition to the inherent dangers associated with each hard docking, a visiting vehicle must be launched into an orbit substantially equivalent to the orbit of the receiving vehicle in order to achieve a hard docking. Payload launch mass performance could be enhanced if the visiting vehicle""s orbit was not required to be as high as the receiving vehicle""s orbit, while still providing a mechanism to transfer payload from the visiting vehicle to the receiving vehicle.
In view of the above, it is an object of the present invention to provide a system which reduces the hazards of rendezvous and payload transfer between an orbiting receiving space vehicle and a visiting space vehicle. It is a further objection to permit rendezvous and payload transfer between a lower orbiting visiting space vehicle and a higher.
The present invention provides an optimized system to deliver cargo to an orbiting receiving space vehicle such as the ISS. The system combines the advantages of the maneuverability of a delivering space vehicle, such as the Space Shuttle, with the large payload capacity of expendable launch vehicles to minimize payload delivery cost. Large payloads are launched into low orbit with expendable launch vehicles. A delivering space vehicle rendezvous with these independently launched payloads and assembles them into a payload stack. The receiving space vehicle located at a higher orbit deploys a tether towards the orbital path of the delivering space vehicle located at a lower orbit, and the tether is used to capture and retrieve the payloads from the delivering space vehicle to the receiving space vehicle.
In a preferred embodiment, a system for underway replenishment of an orbiting receiving space vehicle includes a tether retrieval system coupled to the receiving space vehicle, and at least one orbiting payload adapted to be coupled to the tether retrieval system. The receiving space vehicle captures and retrieves the orbiting payload with the tether retrieval system.
The tether retrieval system preferably includes a tether system base, a tether reel assembly coupled to the tether system base, a tether coupled to the tether reel assembly at a proximal end thereof, and tether distal end component coupled to a distal end of the tether. The distal end component is preferably a free-flying module that is capable of performing independent maneuvers. If desired, the tether retrieval system is further provided with a payload assembly fixture.
A delivering space vehicle used with the system includes a payload assembly fixture, wherein the delivering space vehicle includes means for capturing payloads in Earth orbit and installing the payloads on the payload assembly fixture to form a payload stack.
In operation, the delivering space vehicle and at least one payload are launched into Earth orbit. The payload is captured and installed onto the payload assembly fixture provided in the delivering space vehicle. The delivering space vehicle is manuevered into proximity with the receiving space vehicle including the tether retrieval system. The tether retrieval system of the receiving space vehicle is used to transfer the payload from the delivering space vehicle to the receiving space vehicle.
Other advantages and features of the invention will become apparent from the following detailed description of the preferred embodiments and the accompanying drawings.